This invention relates to certain aromatic polyesteramides which exhibit desirable melt processability and which are useful in the production of films and fibers. More particularly, it relates to aromatic polyesteramides containing repeating 2,2'-substituted biphenylene radicals and aromatic radicals capable of providing ester and amide linkages, for the realization of anisotropic melt phases at temperatures of approximately 360.degree. C. and lower, and preferably, below approximately 300.degree. C.
The production of polyamides, polyesters and polyesteramides suitable for high strength service without the use of reinforcing agents has been well known. These polymers have been variously described as being "liquid crystalline", "thermotropic", "mesogenic", and "anisotropic". In general, these polymers are thought to be characterized by parallel ordering of their molecular chains and are prepared from monomers which are generally long, flat and fairly rigid along the long axis of the molecule. The monomers commonly have chain-extending linkages that are coaxial or parallel. Numerous patents and publications describing polyesters, polyamides and polyesteramides are cited, for example, in U.S. Pat. No. 4,351,918, issued Sept. 28, 1982 to L. F. Charbonneau, et al.
In general, it is well recognized that the mechanical and physical properties of polymeric films and fibers will depend upon the chemical structure of the monomers from which they are prepared and that such properties can be materially influenced by such molecular factors as chain stiffness, intermolecular forces, orientation and crystallinity. Accordingly, there has been considerable interest in the development of polyesters, polyamides and polyesteramides, having particular structural or molecular configurations for the realization of one or more particular properties suited to a desired application. Notably, there has been particular interest in the development of melt processable polymers capable of forming an anisotropic melt phase and suited to processing into films and fibers.
In the production of melt-processed films and fibers from polyesters and polyesteramides, melt processability is frequently hampered by the tendency of such materials to be melt processable only at elevated temperatures which, in some instances, may approach the onset of thermal degradation. In U.S. Pat. 4,575,547 (issued Mar. 11, 1986 to H.G. Rogers, et al.), and in U.S. Pat. 4,608,429 (issued Aug. 6, 1986 to H.G. Rogers, et al.), aromatic polyesters suited to melt processing into films and fibers are described. The polyesters of these patents are especially advantageous from the standpoint of their processability at lower temperatures, e.g., in the range of about 115.degree. C. to to 250.degree. C. The improved melt processability of these polyesters, relative to aromatic polyesters in general, which are only melt processable at higher temperatures, permits improved handling of the polymers and allows for the production of polymeric films and fibers. Frequently, however, it will be advantageous that a polymeric material exhibit a desirable balance of mechanical properties suitable for high strength service, while still being adapted to processing into films and fibers by general molding and melt processing methods without the need for solvent materials and the handling and recovery thereof. It will be appreciated that the advantageous properties of a polyesteramide suited to high strength service will be more readily realized where the polyesteramide material can be readily melt processed into films and fibers at practical processing temperatures.